0.94 (K0.5Na0.5) NbO3–0.06 LiNbO3 piezoelectric ceramics prepared from the solid state reaction modified with polyvinylpyrrolidone (PVP) of different molecular weights

Lead-free piezoelectric 0.94(K0.5Na0.5)NbO3–0.06LiNbO3 (0.94KNN–0.06LN) ceramics were prepared by solid state reaction process modified by introducing polyvinylpyrrolidone (PVP) of different molecular weights in the starting raw materials. The chemical interaction between the metal cations and the PVP, particularly through the N in PVP, was observed. The effects of PVP for suppressing the loss of alkali ions, promoting the perovskite phase formation, and improving the piezoelectric properties were characterized and discussed. With molecular weight ranging from 55 K to 1300 K, PVP with lower molecular weight exhibited more significant effect. This study showed that introducing PVP in the starting raw materials may be an effective method for obtaining stoichiometric KNN–LN and other ceramics with volatile alkali ions.